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net: ip: Fix low Zperf UDP throughput with -a

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When run the Zperf UDP throughput with '-a' (Asynchronous call),
zperf_work_q thread will generate and send the packets to tx_q thread.
When zperf_work_q and tx_q threads have same priority, if zperf_work_q
fails to take the semaphore of fifo_slot, it will not wait and directly
drop the net_pkt. Then it will allocate new net_pkt, repeat, and always
occupy the CPU, which leads to extreme low throughput.
For TX, when take the semaphore of fifo_slot, setting a wait time of
K_FOREVER to let other thread to process and free these packets.
For RX, when failed to take the semaphore of fifo_slot, yield the CPU
to let the thread of data path with same priority to run to reduce
dropping packets.

Signed-off-by: Maochen Wang <maochen.wang@nxp.com>
This commit is contained in:
Maochen Wang 2025-02-17 18:56:48 +08:00 committed by Benjamin Cabé
parent 008a7ca202
commit 2b2915bd98
1 changed files with 17 additions and 3 deletions
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20
subsys/net/ip/net_tc.c
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@ -40,6 +40,9 @@ BUILD_ASSERT(NET_TC_TX_SLOTS > 0,
"CONFIG_NET_TC_TX_COUNT or disable CONFIG_NET_TC_TX_SKIP_FOR_HIGH_PRIO");
#endif
#if NET_TC_RX_EFFECTIVE_COUNT > 1
#define NET_TC_RETRY_CNT 1
#endif
/* Template for thread name. The "xx" is either "TX" denoting transmit thread,
* or "RX" denoting receive thread. The "q[y]" denotes the traffic class queue
* where y indicates the traffic class id. The value of y can be from 0 to 7.
@ -68,7 +71,7 @@ enum net_verdict net_tc_submit_to_tx_queue(uint8_t tc, struct net_pkt *pkt)
net_pkt_set_tx_stats_tick(pkt, k_cycle_get_32());
#if NET_TC_TX_EFFECTIVE_COUNT > 1
if (k_sem_take(&tx_classes[tc].fifo_slot, K_NO_WAIT) != 0) {
if (k_sem_take(&tx_classes[tc].fifo_slot, K_FOREVER) != 0) {
return NET_DROP;
}
#endif
@ -85,11 +88,22 @@ enum net_verdict net_tc_submit_to_tx_queue(uint8_t tc, struct net_pkt *pkt)
enum net_verdict net_tc_submit_to_rx_queue(uint8_t tc, struct net_pkt *pkt)
{
#if NET_TC_RX_COUNT > 0
#if NET_TC_RX_EFFECTIVE_COUNT > 1
uint8_t retry_cnt = NET_TC_RETRY_CNT;
#endif
net_pkt_set_rx_stats_tick(pkt, k_cycle_get_32());
#if NET_TC_RX_EFFECTIVE_COUNT > 1
if (k_sem_take(&rx_classes[tc].fifo_slot, K_NO_WAIT) != 0) {
return NET_DROP;
while (k_sem_take(&rx_classes[tc].fifo_slot, K_NO_WAIT) != 0) {
if (retry_cnt == 0) {
return NET_DROP;
}
retry_cnt--;
/* Let thread with same priority run,
* try to reduce dropping packets
*/
k_yield();
}
#endif